The present invention relates to an electronic component mounting apparatus and electronic component mounting method for mounting electronic components of, for example, semiconductor bare chips, electronic circuit packages and the like onto a board.
Conventionally, in mounting an electronic component such as a semiconductor bare chip with bumps onto a board, there has been adopted a method for bonding the bumps to electrodes on the board by applying a load to the electronic component against the electrodes. According to this method, it is required to control a value of a load applied to each bump within a prescribed range, and therefore, mounting of the electronic component has been performed while measuring a load applied to the electronic component by use of a load sensor such as a load cell.
FIG. 12 shows a construction of a conventional electronic component mounting apparatus. In conventional electronic component mounting apparatus 100, a movement block that moves in a Z-direction is divided into a first movement block 110 and a second movement block 120, and a nut section 121 provided in the second movement block 120 is meshed with a feed screw 151 that is rotationally driven by a motor 150. Moreover, the first movement block 110 and the second movement block 120 are joined so as to be pulled together by a spring 122, and a load cell 130, which is a load sensor, is provided between the first movement block 110 and the second movement block 120. A slider 111 is provided on a side surface of the first movement block 110 and slides on a guide rail 112 provided in the Z-direction.
A lower end portion of the first movement block 110 is provided with a shaft 113, whose central axis is arranged in the Z-direction, and a holding head 115 for sucking and holding an electronic component 101 by a negative pressure, in this order. Moreover, a table 140 movable in an X-direction and a Y-direction is provided below the holding head 115, and a board 102 is placed on the table 140. An output of the load cell 130 is inputted to a control section 160, and the control section 160 controls driving of the motor 150 while monitoring an output of the load cell 130.
When mounting the electronic component 101 onto the board 102, the motor 150 is rotationally driven in a prescribed direction to move down the second movement block 120 and the first movement block 110 in the Z-direction. When the electronic component 101 is brought into contact with the board 102, a load detected by the load cell 130 gradually increases, and the electronic component 101 is pressurized. At this time, by applying, for example, ultrasonic waves while pressurizing the electronic component 101 with a prescribed load, bumps 101a provided at a bottom of the electronic component 101 are connected to a wiring pattern on the board 102 and then mounted. Subsequently, the holding head 115 is separated from the electronic component 101, and the second movement block 120 and the first movement block 110 are moved up in the Z-direction.
As a prior art relevant to the conventional electronic component mounting apparatus, Japanese unexamined patent publication No. 10-163273 discloses an electronic component mounting apparatus in which the first movement block and the second movement block are joined together via an air cylinder instead of joining the first movement block and the second movement block together by a spring. Japanese unexamined patent publication No. 08-203966 discloses an electronic component mounting apparatus in which a voicecoil motor is employed in place of the motor and screw feed mechanism in order to move the movement block in the Z-direction, and the holding head is attached to a shaft driven in the Z-direction by the voicecoil motor. Further, in Japanese unexamined patent publication No. 08-203966, a pressurizing force is estimated from a current applied to the voicecoil motor using no load sensor like the load cell.
Japanese unexamined patent publication No. 11-297764 discloses an electronic component mounting apparatus in which an electronic component and a board surface are made parallel to each other by detecting a pressure during bonding by use of load sensors provided in a plurality of places on a holding head side and adjusting an inclination of a lower surface of the holding head so that a value of the pressure becomes uniform.
Japanese unexamined patent publication No. 04-94553 discloses an electronic component mounting apparatus in which, in a bonding device for performing bonding by pressurizing a tape board against an electronic component placed on a table with bumps directed upward, inclination of the table is adjusted so that a pressurizing surface of a bonding tool and a bonding surface of the electronic component become parallel to each other on the basis of pressurizing forces detected by strain gauges provided in a plurality of places of the bonding tool that holds the tape board. Japanese unexamined patent publication No. 04-223349 discloses an electronic component mounting apparatus in which inclination of a stage is adjusted on the basis of outputs of load sensors provided in a plurality of places of a table. Further, Japanese unexamined patent publication No. 04-223349 discloses a technique for making a pressurizing force of a bonding tool coincide with a pressurizing pattern by performing feedback control on the basis of an output of another load sensor provided for a bonding tool.
In the conventional electronic component mounting apparatus 100 shown in FIG. 12, the load cell 130 is positioned between the first movement block 110 and the second movement block 120, and the slider 111 and the guide rail 112 are provided on a (−Z) side (lower side) of the load cell 130. Generation of some degree of sliding resistance (e.g., about 30 gf) cannot be avoided when the slider 111 slides on the guide rail 112, and a load detected by the load cell 130 includes an error due to this sliding resistance. Therefore, if driving of the motor 150 is controlled on the basis of the load detected by the load cell 130, then there occur variations in a load applied to the electronic component 101. If a load actually applied to the electronic component 101 is extremely smaller than a required load, then a sufficient strength for bonding between the electronic component 101 and the board 102 cannot be obtained, thereby possibly causing contact failure or the like. Conversely, if a load actually applied to the electronic component 101 is extremely larger than a required load, there is the possibility of occurrence of collapse of bumps 101a at a bottom of the electronic component 101 or damage of the electronic component 101 itself.
Moreover, since only a load in the Z-direction is detected by the load cell 130 in the electronic component mounting apparatus 100, if the electronic component 101 is inclined with respect to a surface of the board 102, then a load is not uniformly applied to the bumps 101a at the bottom of the electronic component 101, thereby possibly causing contact failure of some bumps and collapse of some bumps. Such an issue occurs similarly in the electronic component mounting apparatus of Japanese unexamined patent publication No. 10-163273. Moreover, a load applied to the electronic component is detected only in the Z-direction also in the electronic component mounting apparatus of Japanese unexamined patent publication No. 08-203966, and measurement is performed indirectly. Accordingly, there are possibilities of contact failure between an electronic component and a board, collapse of bumps and damage of the electronic component itself.
In the electronic component mounting apparatuses of Japanese unexamined patent publication Nos. 11-297764, 04-94553 and 04-223349, it is possible to detect an inclination of an electronic component and a board by use of a plurality of load sensors arranged in a horizontal detection. However, it is required to separately provide the load sensors in a plurality of places of the apparatus in order to appropriately measure a load. Conversely, if the load sensors are separated from a mounting position, regions occupied by the load sensors are disadvantageously increased. That is, according to a technique of arranging a plurality of load sensors in a horizontal direction, there is a limit to accuracy of sensor sections in detecting inclination of an electronic component with respect to a board surface, and it becomes difficult to accurately detect a mounting failure.
Moreover, in order to remove the above issue that when the electronic component 101 is inclined with respect to the surface of the board 102, the load is not uniformly applied to the bumps 101a at the bottom of the electronic component 101, thereby possibly causing a contact failure of some bumps and collapse of some bumps, it is possible to use, for example, an air bearing in order to reduce sliding resistance when the movement block is moved in the Z-direction. However, although a load can be supported by the air bearing when the load applied to the electronic component is small (e.g., about 300 gf), the air bearing cannot be used when a load that exceeds a prescribed limit is applied. Such issue occurs similarly in the electronic component mounting apparatus of Japanese unexamined patent publication No. 10-163273.
In the electronic component mounting apparatus of Japanese unexamined patent publication No. 08-203966, the holding head is moved while being attached to the shaft driven in the Z-direction by the voicecoil motor, and therefore, a sliding resistance is generated similarly to the case of FIG. 12. Moreover, since a load applied to the electronic component is indirectly measured, there are possibilities of occurrence of a contact failure between an electronic component and a board, collapse of the bumps and damage of the electronic component itself, as described above.
Likewise, in the electronic component mounting apparatuses of Japanese unexamined patent publication Nos. 11-297764, 04-94553 and 04-223349, a load applied to an electronic component is indirectly measured by an inclination adjustment mechanism or the like, and therefore, it is difficult to accurately measure a load actually applied to the electronic component. Therefore, it is difficult to accurately perform adjustment of inclination of an electronic component with respect to a board surface on the basis of outputs from the load sensors, and there is a limit to prevention of a mounting failure of the electronic component with an improvement in accuracy. Moreover, it is required to separately provide load sensors in a plurality of places of the apparatus in order to improve measurement accuracy of a load, and it is difficult to detect the load in the neighborhood of a mounting position.
The present invention has been accomplished to solve the aforementioned conventional issues and has an object to provide an electronic component mounting apparatus capable of accurately detecting a mounting failure of an electronic component by detecting a load in a neighborhood of a mounting position.
Another object of the present invention is to solve the aforementioned conventional issues and provide an electronic component mounting apparatus capable of accurately measuring a load actually applied to an electronic component by eliminating influence of an error due to sliding resistance when a movement block moves.